Elymus wiegandii
Elymus riparius
northern riverbank wildrye, Wiegand's wild-rye, élyme de Wiegand
eastern riverbank wild-rye, river wild-rye, riverbank wildrye, élyme des rivages
100-180(220) cm, erect;
nodes 9-16, mostly concealed by the leaf sheaths, glabrous.
70-160 cm, erect, sometimes rooting at the lower nodes;
nodes 5-10, mostly concealed, glabrous.
evenly distributed;
sheaths usually glabrous, occasionally villous, often reddish brown;
auricles 1-3 mm, brown;
ligules to 1 mm;
blades (8)10-20(24) mm wide, flat, lax, dark green, adaxial surfaces usually thinly pilose, with weakly spreading hairs on the veins at least near the margins, sometimes villous or glabrous.
evenly distributed;
sheaths usually glabrous or scabridulous, often reddish brown;
auricles absent or to 2 mm, brown;
ligules shorter than 1 mm;
blades (5)8-15(25) mm wide, flat, lax, dull green, drying to grayish, adaxial surfaces glabrous or scabrous.
10-30 cm long, 3-5 cm wide, pendent, the bases often barely exserted, with 2 spikelets per node;
internodes 5-8(12) mm long, 0.2-0.3 mm thick at the thinnest sections, usually pubescent beneath the spikelets.
7-25 cm long, 2-4 cm wide, nodding, exserted, usually with 2 spikelets per node, rarely with 3 at some nodes;
internodes 3-5(8) mm long, 0.2-0.35 thick at the thinnest sections, usually glabrous below the spikelets.
12-20 mm, divergent, with (3)4-6(7) florets, lowest florets functional;
disarticulation above the glumes and beneath each floret.
10-20 mm, strongly divergent, with 2-3(4) florets, lowest florets functional;
disarticulation above the glumes and beneath each floret.
equal or subequal, 12-30 mm including the often undifferentiated awns, the basal 0.5-1 mm subterete and slightly indurate, glume bodies 7-12 mm long, (0.2)0.4-0.9(1.1) mm wide, linear-setiform, entire, widening or parallel-sided above the base, 1-3(5)-veined, glabrous, hispidulous or villous, especially near the margins, margins firm, awns (5)8-15(18) mm, straight or flexuous;
lemmas 10-15 mm, usually uniformly appressed-villous, rarely scabrous-hirtellous or glabrous, awns 15-25(30) mm, moderately to strongly outcurving;
paleas 9-14 mm, narrowly truncate, minutely bidentate;
anthers 2-3.5 mm.
equal or subequal, 14-30 mm including the sometimes undifferentiated awn, the basal 0.5-2 mm terete, indurate, straight or nearly so, veins not evident, glume bodies 9-17 mm long, (0.3)0.5-0.8(1) mm wide, linear-setiform, entire, widening or parallel-sided above the base, 2-3(4)-veined, usually hispidulous or scabrous, rarely glabrous, margins firm, awns (5)8-18 mm, straight;
lemmas 7-14 mm, usually hispidulous, sometimes scabrous, awns 15-35 mm, usually straight, those of the basal spikelets occasionally contorted;
paleas 6-9 mm, usually acute, sometimes obtuse to truncate, bidentate;
anthers 2-2.7 mm.
from mid-July to early August.
late June to late July.
= 28.
= 28.
Elymus wiegandii
Elymus riparius
Elymus wiegandii grows in moist or damp, rich, alluvial soil, especially on sandy river terraces and in woods and thickets, primarily from Saskatchewan through much of the Great Lakes region to Nova Scotia and Connecticut. It has abnormal neocentric chromosomes with meiotic irregularities that appear to limit the fertility of its hybrids, and even some crosses within the species (Vilkomerson 1950). It may be derived from hybrids between E. canadensis (p. 303) and perhaps E. riparius (p. 302). The latter species is similar to E. wiegandii and overlaps with it in range and habitat within the Great Lakes region, where there are a few plants that appear to be hybrids between the two. Plants with scabrous-hirtellous or glabrous lemmas (E. wiegandii f. calvescens Fernald) are known from Maine and New Hampshire.
Elymus wiegandii is often confused with sympatric E. canadensis and E. diversiglumis (p. 316), but it has a distinctive robust, broad-leaved habit. It is intermediate between the two in spike density and glume development. Occasional plants with glabrous leaves and less pendent spikes suggest introgression from E. canadensis, but artificial crosses produced no fertile Fj plants (Church 1958).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Elymus riparius grows in moist, usually alluvial and often sandy soils in woods and thickets, usually along larger streams and occasionally along upland ditches. It is widespread in most of temperate east-central North America. It is rare in southern Ontario and Quebec, and the eastern Great Plains. It is virtually absent from the southeastern coastal plain.
Elymus riparius is relatively uniform and distinct. It is sometimes confused with E. canadensis (see next), but that species has curving awns. It hybridizes occasionally with several other taxa, especially E. virginicus var. virginicus (p. 300) and E. hystrix (p. 316), but the hybrids produce only late, depauperate spikes or none at all (e.g., Church 1958).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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